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std::forward_as_tuple(3)       C++ Standard Libary	std::forward_as_tuple(3)

NAME
     std::forward_as_tuple - std::forward_as_tuple

Synopsis
	Defined in header <tuple>
	template<   class...  Types  >					  (since
     C++11)
	tuple<Types&&...> forward_as_tuple( Types&&... args )	      (constexpr
     since C++14)
	noexcept;

	Constructs  a  tuple of references to the arguments in args suitable for
     forwarding as
	an argument to a function. The tuple has rvalue reference  data  members
     when rvalues
	are used as arguments, and otherwise has lvalue reference data members.

Parameters
	args - zero or more arguments to construct the tuple from

Return value
	A std::tuple object created as if by
	std::tuple<Types&&...>(std::forward<Types>(args)...)

Notes
	If the arguments are temporaries, forward_as_tuple does not extend their
     lifetime;
	they have to be used before the end of the full expression.

Example
     // Run this code

      #include <iostream>
      #include <map>
      #include <tuple>
      #include <string>

      int main()
      {
	  std::map<int, std::string> m;

	  m.emplace(std::piecewise_construct,
		    std::forward_as_tuple(10),
		    std::forward_as_tuple(20, 'a'));
	  std::cout << "m[10] = " << m[10] << '\n';

	  // The following is an error: it produces a
	  // std::tuple<int&&, char&&> holding two dangling references.
	  //
	  // auto t = std::forward_as_tuple(20, 'a');
	  // m.emplace(std::piecewise_construct, std::forward_as_tuple(10), t);
      }

Output:
      m[10] = aaaaaaaaaaaaaaaaaaaa

See also
	make_tuple  creates  a	tuple object of the type defined by the argument
     types
	(C++11)    (function template)
	tie	   creates a tuple of lvalue references or unpacks a tuple  into
     individual
	(C++11)    objects
		   (function template)
	tuple_cat  creates a tuple by concatenating any number of tuples
	(C++11)    (function template)
	apply	   calls a function with a tuple of arguments
	(C++17)    (function template)

http://cppreference.com 	   2024.06.10		std::forward_as_tuple(3)
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